You can set the size of the personalized signature word by the following steps:

1. Find the "WeChat" application on the mobile phone's main interface.

2. Find the "I" option in WeChat and enter the "I" interface.

3. Click the "Settings" button in the "Me" interface.

4. Click the "General" option in the "Settings" interface.

5. Click the "Font Size" option in the "General" interface.

6. Slide the axis in the font size interface and set your favorite font size.

The above are the steps to set the size of personalized signature words, I hope it will help you.